Performance

The EPSTM RTLS technology offers sub-meter accuracy in indoor and outdoor environments and can maintain this accuracy over hundreds of meters.

Sub-meter accuracy, long range of operation, resistant to multi-path or interference from reflected signals.

Standard Configuration

A minimum EPSTM RTLS installation involves four EPSTM Reference Nodes with fixed positions, one EPSTM Gateway Node with LAN or USB data connection to a computer server running the EPSTM Tracker Server Location Engine, and several EPSTM Mobile Nodes (Tags) of which the positions are tracked.

Operation

A radio signal is transmitted back and forth between an EPSTM Mobile Node and the EPSTM Reference Nodes. This is known as Two-Way-Ranging (TWR).

The EPSTM technology measures the Time-of-Flight (ToF) of the radio signal, or the length of time it takes for the radio signal to travel between the radio nodes. This information is used to calculate the distance between the Mobile Node and each of the Reference Nodes.

The Location Engine in the EPSTM Tracker Server converts the distance measurements to positions. The EPSTM Tracker Server also manages the RTLS network and provides an interface for various Client Applications to access the position coordinates.

Sub-meter Accuracy

The EPSTM HW is capable of resolving time differences better than 3 ns yielding distance accuracies below 1 meter. This accuracy is further improved by signal processing techniques.

The steep rising edge of the RF-burst, used to define the time-of-flight, makes it possible to measure exactly the time when the signal arrives at the mobile node or vice-versa. Even when the signal is attenuated due to the large travel distance, or perturbed by reflections, the first edge observed at the receiver will have traveled the shortest distance.

In the case of the EPS TM technology, this time of arrival is measured with better than 3ns resolution, resulting in a single shot resolution of 0.3m for a round trip. With averaging techniques this resolution is further improved. The final error on the distance measurement depends mainly on the steepness of the edge. Larger distances or heavy obstructions attenuate the peak amplitude of the burst but maintain the edge transition time. Since this edge transition time is max 3ns, the uncertainty on the time-of-flight in Line-of-Sight versus obstructed Non-Line-of-Sight is max 3ns, or 1 meter in distance.

The distances are sent to a tracker server, where advanced and proprietary positioning algorithms calculate the position of a mobile node from a set of distance measurements. With careful configuration of the deployment and thanks to the use of the powerful localization algorithms, the position accuracy is typically 50cm or better. Redundancy is leveraged to derive the position with high accuracy even under very bad conditions of interferences and obstructions.

Patented Technology

Traditional wireless RTLS technologies can be split into two main subgroups, Wideband and Narrowband, depending on the radio frequency bandwidth used. Each approach has its own particular advantages and disadvantages.

Essensium´s patented approach combines the benefits of both Narrowband and Wideband behaviour in a single Wide-over-Narrowband RF implementation. This results in an industry-leading RTLS implementation giving both the accuracy of a very precise UWB system combined together with long range, and thus lower infrastructure costs, better than that of typical narrowband or WiFi methods for RTLS. This combination of attributes enables exciting opportunities for track and trace applications, both indoors and outdoors.

Wideband methods, typically known as UWB, tend to yield highly accurate position detection, with a resolution down to 10´s of centimeters, but support only a very limited distance between the tag and the readers. This limits their useful application to situations where items need to be tracked over a relatively small area, since a significant and expensive infrastructure of reader antennae needs to be added in order to cover larger areas.

Narrowband methods, typically known as WiFi or RSSI methods, tend to support much larger distances between the tracked item and the readers. This allows larger areas to be covered compared to UWB, with a more affordable infrastructure cost. These methods suffer from the disadvantage of having significantly lower resolution, allowing only to determine the position of a tag with a resolution of several meters at best, or even simply allowing only to identify the room, or zone, in which a particular tag is located.

Essensium´s patented approach combines the benefits of both Narrowband and Wideband behaviour in a single Wide-over-Narrowband RF implementation. This results in an industry-leading RTLS implementation giving both the accuracy of a very precise UWB system combined together with long range, and thus lower infrastructure costs, better than that of typical narrowband or WiFi methods for RTLS. This combination of attributes enables exciting opportunities for track and trace applications, both indoors and outdoors.